Synthesis, Characterization, and Crystal Structures of 4,6-Dimethoxy-2-hydroxy-3-methylbenzoic Acid and 2,4-Dimethoxy-6-hydroxy-3-methylbenzoic Acid

摘要

A synthetic route involving 4,6-dimethoxy-2-hydroxy-3-methylbenzoic acid (10) and 2,4-dimethoxy-6-hydroxy-3-methylbenzoic acid (11) has been investigated in the process of synthesis of the natural lichen substance namely, crocynol. Crystal structures of 10 and 11 were determined to confirm the ambiguous structures of the two isomers. Crystals 10 are monoclinic, sp. gr. P2(1)/m, Z = 2. Crystals 11 are monoclinic, sp. gr. P2(1)/c, Z = 4. In the crystal packing of 10, the molecules are arranged into chains along the a-axis formed only by van der Waals interactions, whereas in 11, the molecules are linked by O-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds into chains along the b-axis and further stacked by pi center dot center dot center dot pi interactions with the centroid center dot center dot center dot centroid distance of 3.6863(8)angstrom .